2018-05-30 08:15:50 +00:00
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use crate::consts::{constant_simple, Constant};
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2016-04-07 15:46:48 +00:00
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use rustc::hir::*;
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2018-08-28 11:13:42 +00:00
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use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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2018-07-29 09:04:40 +00:00
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use rustc::{declare_tool_lint, lint_array};
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2018-08-20 02:06:53 +00:00
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use syntax::source_map::Span;
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2018-05-30 08:15:50 +00:00
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use crate::utils::{in_macro, snippet, span_lint, unsext, clip};
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2018-03-13 10:38:11 +00:00
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use rustc::ty;
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2015-07-09 15:02:21 +00:00
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2016-08-06 07:55:04 +00:00
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/// **What it does:** Checks for identity operations, e.g. `x + 0`.
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2015-12-11 00:22:27 +00:00
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///
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2016-08-06 07:55:04 +00:00
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/// **Why is this bad?** This code can be removed without changing the
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/// meaning. So it just obscures what's going on. Delete it mercilessly.
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2015-12-11 00:22:27 +00:00
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///
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2016-08-06 07:55:04 +00:00
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/// **Known problems:** None.
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2015-12-11 00:22:27 +00:00
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///
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2016-07-15 22:25:44 +00:00
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/// **Example:**
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/// ```rust
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/// x / 1 + 0 * 1 - 0 | 0
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/// ```
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2018-03-28 13:24:26 +00:00
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declare_clippy_lint! {
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2016-08-06 08:18:36 +00:00
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pub IDENTITY_OP,
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2018-03-28 13:24:26 +00:00
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complexity,
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2016-02-05 23:13:29 +00:00
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"using identity operations, e.g. `x + 0` or `y / 1`"
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}
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2015-08-11 18:22:20 +00:00
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2017-08-09 07:30:56 +00:00
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#[derive(Copy, Clone)]
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2015-05-15 16:46:43 +00:00
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pub struct IdentityOp;
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impl LintPass for IdentityOp {
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fn get_lints(&self) -> LintArray {
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lint_array!(IDENTITY_OP)
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}
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2015-09-19 02:53:04 +00:00
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}
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2015-05-22 22:49:13 +00:00
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2016-12-07 12:13:40 +00:00
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for IdentityOp {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
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2017-03-31 22:14:04 +00:00
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if in_macro(e.span) {
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2016-01-04 04:26:12 +00:00
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return;
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}
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2018-07-12 07:30:57 +00:00
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if let ExprKind::Binary(ref cmp, ref left, ref right) = e.node {
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2015-05-22 22:49:13 +00:00
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match cmp.node {
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2018-07-12 07:50:09 +00:00
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BinOpKind::Add | BinOpKind::BitOr | BinOpKind::BitXor => {
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2015-05-22 22:49:13 +00:00
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check(cx, left, 0, e.span, right.span);
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check(cx, right, 0, e.span, left.span);
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2016-12-20 17:21:30 +00:00
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},
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2018-07-12 07:50:09 +00:00
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BinOpKind::Shl | BinOpKind::Shr | BinOpKind::Sub => check(cx, right, 0, e.span, left.span),
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BinOpKind::Mul => {
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2015-05-22 22:49:13 +00:00
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check(cx, left, 1, e.span, right.span);
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check(cx, right, 1, e.span, left.span);
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2016-12-20 17:21:30 +00:00
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},
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2018-07-12 07:50:09 +00:00
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BinOpKind::Div => check(cx, right, 1, e.span, left.span),
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BinOpKind::BitAnd => {
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2015-05-22 22:49:13 +00:00
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check(cx, left, -1, e.span, right.span);
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check(cx, right, -1, e.span, left.span);
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2016-12-20 17:21:30 +00:00
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},
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2016-01-04 04:26:12 +00:00
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_ => (),
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2015-05-22 22:49:13 +00:00
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}
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}
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2015-05-15 16:46:43 +00:00
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}
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}
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2018-08-01 20:48:41 +00:00
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#[allow(clippy::cast_possible_wrap)]
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2018-07-23 11:01:12 +00:00
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fn check(cx: &LateContext<'_, '_>, e: &Expr, m: i8, span: Span, arg: Span) {
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2018-05-13 11:16:31 +00:00
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if let Some(Constant::Int(v)) = constant_simple(cx, cx.tables, e) {
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2018-03-13 10:38:11 +00:00
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let check = match cx.tables.expr_ty(e).sty {
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2018-08-22 21:34:52 +00:00
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ty::Int(ity) => unsext(cx.tcx, -1_i128, ity),
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ty::Uint(uty) => clip(cx.tcx, !0, uty),
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2018-03-13 10:38:11 +00:00
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_ => return,
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};
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2015-09-06 08:53:55 +00:00
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if match m {
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2018-03-13 10:38:11 +00:00
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0 => v == 0,
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-1 => v == check,
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1 => v == 1,
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2015-09-06 08:53:55 +00:00
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_ => unreachable!(),
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2017-09-05 09:33:04 +00:00
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} {
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2017-08-09 07:30:56 +00:00
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span_lint(
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cx,
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IDENTITY_OP,
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span,
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&format!(
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"the operation is ineffective. Consider reducing it to `{}`",
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snippet(cx, arg, "..")
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),
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);
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2015-08-16 21:09:56 +00:00
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}
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2015-05-22 22:49:13 +00:00
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}
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2015-05-15 16:46:43 +00:00
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}
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